In this
chapter, students will read about the origin of plants and the major characteristics
that distinguish plants from other organisms. They will also read about
the differences among bryophytes, ferns, gymnosperms, and angiosperms
in reproduction and internal transport systems. The links below lead to
additional resources to help you with this chapter. These include Hot
Links to Web sites related to the topics in this chapter, the Take It
to the Net activities referred to in your textbook, a Self-Test you can
use to test your knowledge of this chapter, and Teaching Links that instructors
may find useful for their students.

Section
22-1: Introduction to Plants Plants are multicellular
eukaryotes that have cell walls made of cellulose. They develop from multicellular
embryos and carry out photosynthesis using the green pigments chlorophyll
a and b. The lives of plants revolve around the
need for sunlight, water and minerals, gas exchange, and the movement
of water and nutrients throughout the plant body. The first plants evolved from an organism
much like the multicellular green algae living today.

Section
22-2: Bryophytes Bryophytes have life cycles that depend
on water for reproduction. Lacking vascular tissue, these plants can draw
up water by osmosis only a few centimeters above the ground. Bryophytes include mosses, liverworts,
and hornworts.
In bryophytes, the gametophyte is the dominant, recognizable stage of
the life cycle and is the stage that carries out most of the plant's photosynthesis.

Section
22-3: Seedless Vascular Plants Both forms of vascular tissuexylem
and phloemcan move fluids throughout the plant body, even against
the force of gravity. Seedless vascular plants include club
mosses, horsetails, and ferns. Ferns and other vascular plants have
a life cycle in which the diploid sporophyte is the dominant stage.

Section
22-4: Seed Plants Adaptations that allow seed plants to
reproduce in areas without water include flowers or cones, the transfer
of sperm by pollination, and the protection of embryos in seeds. Gymnosperms include gnetophytes, cycads,
ginkgoes, and conifers.

Section
22-5: AngiospermsFlowering Plants Angiosperms have unique reproductive
organs known as flowers. Flowers contain ovaries, which surround and protect
the seeds. Monocots and dicots are named for the
number of seed leaves, or cotyledons, in the plant embryo. Monocots have
one seed leaf, and dicots have two. There are three categories of plant life
spans: annual, biennial, and perennial.